The present invention is directed to electronic converter circuits which are used to sense indicator signals generated by a towing vehicle and in response drive the lighting circuits of a towed trailer.
Devices for the interface of trailer lights to a towing vehicle are well known. Since towing vehicles started separating the turn signal lamps from the brake signal function, converters have been used to combine the STOP and TURN signals to drive the combination lights typically used on trailers.
Recent innovations in the electrical systems of the towing vehicles have further combined the signal lighting. In these vehicles, a single lamp can be used to indicate a turn signal, a stop signal, and the running light indication by allowing the intensity of the lamp to be controlled. This is done by modulating the energy supplied to the lamp. This could be done by producing multiple different voltages to drive the lamp. More commonly, it is done by driving the lamp using pulse-width modulation (PWM) techniques to efficiently operate the lamp in a dim mode to indicate the running light condition and operate the lamps at 100 percent brightness to indicate a stop or turn.
It is possible to interface a trailer lighting system to a towing vehicle having modulated lighting, such as PWM or variable voltage, using a buffered lighting converter of the type disclosed in my patent application Ser. No. 12/369,207, filed Feb. 11, 2009, for a PROTECTED TRAILER LIGHTING CONVERTER, or other known buffered converter, by locating an appropriate signal wire at whatever location it may be in the vehicle and supplying the converter. The STOP light signal is usually available in the center high mounted stoplight location (CHMSL); RUNNING light signals can be found at the side marker light locations (including the front side markers). Left and right turn lamp signals may be obtained at the dashboard. Installations performed this way may be difficult to complete as these circuits may be long distances away from the required connections to the trailer.